Their orders are to “work with the industry and with the state of California on developing a single national standard so that domestic automakers do not have to comply with two different regulatory regimes,” Helen Ferre, a White House spokesman, said Monday.

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California is the nation's largest car market, which has long set stricter car emissions targets than the federal government. The two standards would have been aligned under new fuel efficiency regulations set in place by the Obama administration in 2012 requiring new cars and trucks to get 54.5 miles per gallon by 2025.

Such a standard would almost certainly mean losses for the U.S. refining sector, which is centered around Houston and the Gulf of Mexico. In 2012 the White House estimated the new mileage standard would reduce U.S. oil consumption by 2.2 million barrels a day in 2025 — more than 10 percent of the current total.

Oil and gas lobbyists have joined automakers in fighting to block the standard. In 2016 the American Petroleum Institute told the government that the regulation contained “a number of incentives that appear to reflect an attempt to pick winning and losing technologies in the marketplace, an action which could potentially limit consumer choice and increase societal costs.”

Pruitt announced earlier this year that the EPA would revise the Obama-era standard, which he said, “didn’t comport with reality,” and would also be reviewing the decades-old federal waiver that allows California to set tougher air pollution standards than the rest of the country.

Earlier this month, California and 16 other states sued the EPA in an attempt to derail any move to lower car efficiency standards.

“The evidence is irrefutable: Today's clean car standards are achievable, science-based and a boon for hardworking American families,” California Attorney General Xavier Becerra said in a statement. “But the EPA and Administrator Scott Pruitt refuse to do their job and enforce these standards."

That set the stage for a long legal fight, which would leave car manufacturers in limbo awaiting a ruling from the courts.

Trump's move to begin talks with California officials followed a meeting at the White House Friday with the CEOs of General Motors, Ford and Fiat Chrysler, as well as senior executives from other auto manufacturers.

Afterwards, Mitch Bainwol, president of the Auto Alliance, a trade group representing car manufacturers, said in a statement, said the executives “appreciate the President’s openness to a discussion with California on an expedited basis.”